This invention relates to wells, and more particularly, to a method of operating wire line tools to provide for tool release in case of the tool becoming stuck in the well bore.
Previously, when a wire line tool has become stuck in the well bore, it has been the practice to fish the tool out by running pipe in the bore down to the level of the tool, washing away the mud cake in which the tool had gotten stuck, and if the tool remained stuck, retrieving the tool with some device run on the pipe such as an overshot. Compare U.S. Pat. No. 1,858,500--Hinderliter.
In connection with stuck drill pipe and drill collars, when the pipe or collar has become stuck, a variety of methods of releasing the pipe or collar have been employed. For example, the pipe string may be cut off above the stuck point, e.g. with a tool as shown in U.S. Pat. No. 2,167,445--Brown and the free part of the string withdrawn. Thereafter, the remaining stuck pipe can be washed over and then pulled out with a spear or overshot. See for example the disclosure of U.S. Pat. No. 3,800,876--Eggleston. Hydraulic methods of releasing the pipe or collar have been suggested. See for example the disclosures of U.S. Pat. Nos.:
______________________________________ 1,568,027 Swan 2,139,076 Gates 2,808,887 Erwin 3,096,822 Hall 3,104,707 Overly 3,236,307 Brown ______________________________________
It is also known, in the case of stuck pipe (or collars), to introduce a mud active agent into the pipe and pump it to the level where the pipe or collar is stuck; many times the stuck pipe is released. Such a mud active agent may be an acid, e.g. H Cl, to decompose the mud, or a chemical that will shrink the mud particles and allow well liquid to penetrate the mud cake. In either case communication will be established around the pipe to the fluid in the well bore so that the hydrostatic pressure of the well liquid around the stuck tool will become balanced and the lateral pressure imbalance destroyed, thereby freeing the pipe or collar from side thrust pressing it against the side of the hole. Two stuck pipe freeing mud active agents are available to the trade under the tradenames Black Magic and Pipe Lax.
Mud active agents placed by circulating the drilling fluid through pipe are of course unavailable for retrieval of wire line tools in the absence of any pipe through which the agent can be positioned. The total volume of mud in a well bore is too great to treat it all by dumping the agent down the hole. Also, it might be undesirable to change the character of the entire batch of drilling fluid. On the other hand, freeing of stuck wire line tools by washing over and fishing requires the expense of running in drill pipe.